SU1597754A1 - Apparatus for measuring current - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to measure currents in galvanically isolated circuits. The aim of the invention is to increase the dynamic accuracy and reduce power consumption. For this purpose, a pulse shape converter 11, a two-level comparator 12 and a pulse shaper 13 are inserted into the device. Under the influence of the excitation current from the alternating voltage generator 7 flowing in the excitation windings 5 and 6, the cores 1 and 2 are magnetized, which is the sum of the measured current in the windings 3 and 4 and the excitation current. Blocks 11-13 form write pulses that control the operation of a switch 9, which transmits information from a current-to-converter 8 - voltage to memory element 10. One of the cores 1 or 2 is in a saturated state, but the other core is not always saturated. The description provides an example of the implementation of a two-level comparator 12. 3 Il.

Description

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The invention relates to an electrical measuring technique, in particular, to devices for measuring current in galvanically developed circuits.

The purpose of the invention is to increase the dynamic accuracy and reduce power consumption.

FIG. 1 shows the functional scheme of the device; in fig. 2 - an example of a two-level comparator; in fig. 3 - diagrams of signalv.

A device for measuring current (Fig. 1) contains ferromagnetic cores 1. and 2 of a magnetic converter, input windings 3 and 4 ,. connects in series and arranged respectively on the cores 1 and 2, the windings 5 and excitation windings are placed respectively on the cores 1 and 2 and the opposite alternator voltage generator 7 is connected to the start of the excitation winding 5, the current 8 converter is the voltage Connected with its input with the start of the excitation winding 6, the output of the voltage converter 8 - the current through the switch 9 is connected to the input of the element 10. memory, the common outputs of the windings 5 and 6 of the excitation are connected to the input of the pulse form converter 11, the output which through series-connected, two-level comparator 12 and pulse shaper 13 are connected to the control input of the switch 9, the leads of the input windings 3 and 4 are connected to the input terminals 14 and 15, respectively, the output of the memory element 10 is connected to the output terminal 16.

The two-level comparator 12 (FIG. 2) contains current sources 17 and 18, the first terminals of which are grounded, the second output of current source 17 17 is connected to the cathode of dyard 19, the first view of the resistor 20 and the non-inverted input 21 of the operational amplifier 21, Inverting: input connected to the second terminal of the current source 18 50, the diode of the .22 diode and the first terminal of the resistor 23, the second outputs of the resistors 20 and 23 are combined and are the input of a two-level comparator 12, the anode of the diode 19. And the cathode diode, and 22 are grounded, the output of the operating amplifier 21 is output d 12-level comparator 12. V. quality converter 11 pulse shape

.

in the simplest case, an integrating RC circuit can be used.

The device dp current measurement works as follows.

The alternating voltage generator 7 generates rectangular-shaped alternating pulses (Fig. 3A), under the influence of which in the series circuit from the windings 5 and 6 of the excitation and the converter 8 current - voltage, current pulses arise (Fig. 3Sv), whose amplitude is due to - with measured current ratio:

1i

. IB is k; where Ig, 1 | - instantaneous values of excitation currents and measured, respectively; K - transformation ratio.

The excitation current is limited at a level proportional to the current being measured (Fig. 36) due to the fact that at any moment of time one of the cores is in saturation, and the other is the process of magnetization reversal, which is characterized by what is in the core the equality of the MDS from the measured current and the current in the excitation winding (I d 1 (), and under the influence of a voltage applied to the excitation winding of this core, the induction in the core varies, for example, from -Bj to V c, (Fig. ZG.) Duration process peremagn one of the cores in one of the directions is 1/4 of the alternating voltage period of the alternating voltage generator 7 and is a function of the parameters of the core material, the number of turns in the excitation winding and the applied voltage. the polarity of the voltage applied to the winding 6 of the exciter 1-w, and the process of induction change from -B begins, which ends at the moment t and means the transition of the core 2 to the saturated state, and at the same time the output of the core 1 from the saturation state (Fig . Rear). There follows a process of changing induction from B J. to -Hz, and then the processes are repeated in core 2.

A diagram of the currents in the excitation windings 5 and 6 is shown in FIG. Sv, gram of voltage E at the common point of the windings 5 and 6 of the excitation relative to the common point of the circuit - in FIG. Ze,

From the diagrams it follows that the pulses

the voltages at the common point of the windings 5 and 6 of the excitation always correspond to the points in time when the amplitude and polarity of the current pulses. excitations c correspond to the value and sign (direction) of the measured current, increasing the dynamic accuracy by doubling the frequency of writing to the element, Yu the memory of a reliable inL ormap about the measured current, which confers in the output signal of the converter 8, the current - voltage, voltage pulses (Fig. Ze) are passed through the converter 11 of the pulse shape, the two-level comparator 12 and the ovatel 13 pulses and receive at control pulses input key 9 (FIG. Zzh) that twice per period of the alternating voltage generator 7 is determined by the beginning and the finalization of the recording signal in the memory element 10.

FIG. W3 presents the information recorded in the memory element 10 by the magnitude B in the diagrams denotes the magnitude of the induction;

Pa-output two-level comparator 12 there is a logical zero if the input current module is less than the current modules of the current sources 17 and 18. The logical unit at the output of the operational amplifier 21 will be if the directions of the input current and the current of the source 17 or 18 current do not coincide, and the input current module exceeds the current module of the current source 17 or 18. The outcome of the above and.

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According to FIG. 2, the input signal of positive polarity causes the switching of the two-terminal comparator 12 via the non-inverting input of the operational amplifier ll, and the negative one via the center line; Diodes 19 and 22 are restrictive.

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An apparatus for measuring current, comprising a magnetic transducer on two ferromagnetic cores,

each of which is provided with an external winding and a winding, the input windings are connected according to and in series, two of which are the inputs of the device

field windings are connected in opposite and in series, an alternator, the output of which is connected to the beginning of the first field winding, the current converter is voltage, the output of which is connected via a key to the input of the memory element whose output is the output of the device, that, in order to improve the dynamic accuracy and reduce the power consumption, a series-connected pulse shape converter, a two-level comparator and a pulse shaper were inserted into it, and the input reobrazovatel shape im- pulse is coupled to common terminals of the first and second windings 13ozbu sdeni, the pulse shaper output is connected to the control input of the key input - the converter current - voltage, is connected with the beginning of the second excitation winding,

20

17

Claims (1)

Claim A device for measuring current, containing a magnetic transducer on two ferromagnetic cores, each of which is equipped with an input (winding and excitation winding, the input windings connected in series and in series, the two outputs of which are the inputs of the field winding device, connected in opposite and in series, the generator AC voltage, the output of which is connected to the beginning of the first field winding, the current transducer is in memory. In FIG. Зз presents information recorded in the memory element 10. The value of In f, the diagrams indicate the value of the induction of saturation, In _c - the magnitude of the induction in the core at the beginning of the magnetization reversal. At the output of the two-level comparator 12 there is a logical zero if the input current module is less than the current modules of the current sources 17 and 18. The logical unit at the output of the operational amplifier 21 will be if the directions of the input current and current of the current source 17 or 18 do not coincide, and the input current module exceeds the current module of the current source 17 or 18. Based on the foregoing and. 25. voltage, the output of which is connected via a key to the input of a memory element, the output of which is the output of the device, characterized in that, in order to increase dynamic accuracy and reduce power consumption, series-connected pulse shape converter, two-level comparator and driver are introduced into it pulses, and the input of the pulse shape converter 35 is connected to the common terminals of the first and second field windings, the output of the pulse shaper is connected to the control input of the key, the input 40 of the current-voltage converter is connected to the beginning of the second field winding. health b) 1 „a ·} Ur d) B2 ^ _c , Jt k _t ¹ , τ h rtf CM '4? 3) 82 ^ 8 ,. MblYYI-Gv * S) B2k * B _r e) E ! gkp Π. Π π 1 J Π R .L Li Ί 1 L LT j U J.J L LTI eleven Li L Γυ eleven ΓΊΠ 1 L ± ^ J t t